On 08/01/2018 16:26, Arnd Bergmann wrote:

On Fri, Jan 5, 2018 at 10:31 AM, Daniel Lezcano
[off-list ref] wrote:

quoted

quoted

quoted

No. Can't you add in arch/ndis32/Kconfig ?

+select TIMER_ATCPIT100

Like:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/Kconfig#n50

IMHO, it might be a little bit wierd if we select TIMER_ATCPIT100 in
arch/nds32/Kconfig because it is part of SoC instead of CPU.
If we change to another SoC with another timer, we need to select
another TIMER in arch/nds32/Kconfig and delete TIMER_ATCPIT100.
It seems more flexible to be selected in driver layer.

It seems to be the timer is part of the arch to be selected in arch's Kconfig.
arch/arc/Kconfig:       select ARC_TIMERS
arch/arc/Kconfig:       select ARC_TIMERS_64BIT
arch/arm/Kconfig:       select ARM_ARCH_TIMER
arch/arm64/Kconfig:     select ARM_ARCH_TIMER
arch/blackfin/Kconfig:  select BFIN_GPTIMERS

No, the timer must be selected from the arch/soc's or whatever Kconfig.
Not in the clocksource's Kconfig.

eg.

on ARM:

arch/arm/mach-vt8500/Kconfig:   select VT8500_TIMER
arch/arm/mach-bcm/Kconfig:      select BCM_KONA_TIMER
arch/arm/mach-actions/Kconfig:  select OWL_TIMER
arch/arm/mach-digicolor/Kconfig:        select DIGICOLOR_TIMER

etc ...

on ARM64:

arch/arm64/Kconfig.platforms:   select OWL_TIMER
arch/arm64/Kconfig.platforms:       select ARM_TIMER_SP804
arch/arm64/Kconfig.platforms:       select MTK_TIMER

etc ...

I'd actually prefer to not do it for ARM either: Most other subsystems
don't do that, and I don't see a strong reason why clocksource should
be special here.

The majority doing the opposite does not mean it is right.

Do you know which clock belongs to which board ? Who will unselect a
clock ? I'm pretty sure nobody. Everyone relies on the platform Kconfig
and expect it to select the right drivers.

We don't expect the hackers to have a deep knowledge of the hardware and
the driver dependencies. It is very convenient to not care about that
and let the platform's Kconfig to select the right drivers.

And that is the behavior I would like to keep.

Selecting 'TIMER_OF' from the individual drivers that need it (as you
suggest) makes sense, but I think for ARM we treat SoC families
as a bit too special, in the end they are for the most part collections
of individual hardware blocks that may or may not be present on
some chip.

In case of risc-v and nds32, I expect that the separation will be
even less visibile in the hardware, as a typical model here is
that one company designs SoCs for multiple customers that each
have different requirements. Some of them may have one
timer and some have another timer or multiple timers, but there
is no strict separation between SoC families as I understand.
Here we'd be better off not having a per-SoC Kconfig option at
all, just a generic defconfig that enables all the drivers that might
be used, and integrators can have a defconfig file that only
enables the stuff they actually use on a given chip.

Yes, the result is the same, the option is not showed in the menu.

However, I can understand it could be interesting to have the ability to
unselect a driver for experts.

I'm wondering if we can create a bool_expert which shows up only when
CONFIG_EXPERT is set.




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